1. Field of the Invention
This invention relates to magnetic films having a high permeability in a high frequency range and a low coercive force and more particularly, to multilayered magnetic films which can maintain a high permeability even when processed in the form of a pole and have good magnetic characteristics. The invention also relates to high performance thin-film magnetic heads using the multilayered magnetic films.
2. Description of the Prior Art
For the improvement of high frequency characteristics of magnetic films, there is known a method in which magnetic layers are deposited through a nonmagnetic intermediate layer such as SiO.sub.2. As particularly described in Japanese Laid-open Patent Publication No. 58-192311, it is known that with known multilayered magnetic films such as, for example, a multilayered magnetic film in which Fe-Si layers are superposed through an intermediate layer of a nonmagnetic material such as SiO.sub.2, the grain size of Fe-Si itself becomes smaller by the superposition, so that the dispersion of the anisotropy is suppressed, leading to an improvement of magnetic characteristics of the resultant film. In this case, the thickness is generally in the range of from 0.01 to 0.2 .mu.m for the magnetic films and in the range of from 1 nm to 10 nm for the intermediate layer. This is because when the thickness of the intermediate layer is in the order of several nm, pin holes are essentially present, so that the exchange interaction between the Fe-Si layers are induced through the pin holes and thus the respective layers couple ferromagnetically while suppressing the dispersion of the anisotropy. As a consequence, the film has good magnetic characteristics as a whole.
On the other hand, in order to improve the high frequency characteristics of the multilayered magnetic films, it is necessary to reduce an eddy current loss in the high frequency range. In Japanese Laid-open Patent Publication No. 59-9905 (1984), an attempt was made to improve the high frequency characteristics of the multilayered film by superposing the magnetic layers through a thicker nonmagnetic insulative layer. For improving the high frequency characteristics, it is stated to be desirable that the thickness of the nonmagnetic intermediate layer ranges from 0.05 to 1 .mu.m. However, when such multilayered film is patterned in the form of a pole for application to a thin-film magnetic head, the permeability at 10 MHz lowers to about 1/10 time the permeability of the initial film prior to the patterning. Thus, good head characteristics cannot be obtained.